High-power flexible-polarization in-orbit-calibration satellite payload

ABSTRACT

A system of architecture, apparatus and calibration method is invented for high-power flexible-polarization payload for satellite communications. The system comprises onboard phase-tracked apparatus, flexible polarization mechanism, and in-orbit calibration method. The power combining and polarization performance of the phase-tracked payload is monitored on ground by measuring the cross-polarization discrimination (XPD) and/or axial ratio (AR). The high performance over the life is achieved by optimization of the XPD or AR on ground and adjusting complex gain of the transponders. The high-power flexible-polarization in-orbit-calibration payload may be applied but not limited to UHF, L, S, C, X, Ku and Ka-band high power satellite systems.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. Provisional Application forPatent No. 62/854,150 filed May 29, 2019, the content of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention generally relates to satellite communication systems, andparticularly to the architecture, polarization mechanism, and in-orbitcalibration method for a high-power phase-tracked communication payload.

BACKGROUND OF THE INVENTION

The evolution to more advanced satellite systems, in particular the highdata rate and high confidentiality communication systems, results in aneed of high transmit power and flexible polarization communicationpayloads.

An example of a schematic block-diagram of a generic communicationpayload is shown in FIG. 1. This generic payload comprises adual-polarization antenna, transmit (TX) chain, receive (RX) chain, anda centralized On-Board Processor (OBP) that processes the TX and RXsignals. The transmit chain comprises an up-converter, combinedhigh-power amplifiers and an output filter. The receive chain comprisesan input filter and a receiver. A duplexer is used to segregate the TXand RX signals. A high-power RF (Radio-Frequency) switch is used forantenna polarization selection. Either polarization type “A” orpolarization type “B” can be selected. The polarization can be of anytype: linear, circular, etc.

One drawback of the generic satellite payload (FIG. 1) is that the totaloutput power is limited by the power handling capability of theequipment in the output chain after the power combiner. Another drawbackis that the output combiner and the polarization selection switchintroduce an additional insertion loss in the TX chain that reduces thecommunication data rate. In addition, the switching of the polarizationsmay cause a temporary loss of signals which is unwanted (not desirable)in certain applications.

Accordingly, there is a need of an improved payload architecture,apparatus and calibration method for high-power flexible-polarizationpayload for satellite communications.

SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide animproved payload architecture, apparatus and calibration method forhigh-power flexible-polarization payload for satellite communications,as exemplified in different embodiments shown in FIGS. 2 to 10, toobviate the above-mentioned drawbacks and problems of the common payload(an example of which being shown in FIG. 1).

An advantage of the present invention is that the high-powerflexible-polarization in-orbit-calibration payload may be applied butnot limited to high power satellite systems operating at UHF, L, S, C,X, Ku and Ka-band signal frequencies of the RF/microwave signals.

The present invention provides a system architecture, onboard and/orground calibration apparatus and method for high-powerflexible-polarization payload for satellite communications. Anotheradvantage of the present invention is that the system comprises onboardphase-tracked apparatus, flexible polarization mechanism, and in-orbitcalibration method to allow calibration over time and temperaturevariations. The invention is applicable to satellite communications insimplex, half-duplex or full duplex modes.

A further advantage of the present invention is that the onboardphase-tracked payload of the current invention applies the powercombining at the antenna aperture (RF waves from both X and Y componentsare coherently added at antenna aperture, in space, and, by changing theamplitude and phase of each component, the polarization of the combinedwaves can be controlled to obtain the Left-Hand Circular Polarization(LHCP) or Right-Hand Circular Polarization (RHCP) and the performancedegradation can be calibrated), thus significantly increasing thehigh-power capability of the system. In addition, the RF power combinerand high-power switch are no longer needed, therefore reducing the TXoutput circuit insertion losses. Furthermore, the polarization selectionswitch may be implemented within the OBP, permitting seamless switchingwithout any loss of RF signal during polarization selection switching,thereby providing increased communication security.

Yet another advantage of the present invention is that it also providesa system of calibrating a communication payload, the system comprising:providing a means to measure the cross-polarization discrimination (XPD)and/or axial ratio (AR) by ground systems; providing a means to optimizeXPD/AR performance using ground computer; up-linking the calculated gainand phase adjustment data via a conventional or payload-specifictelecommand (TC) link, whichever is available; and providing a means tovary output signal gain (amplitude) and phase on the payload transmitpath using OBP or Gain & Phase Adjusters.

A further advantage of the present invention is that whenever the TX andRX frequencies can be directly processed by the OBP, the functions ofthe low power electronics such as up-converters and receivers can beincorporated into the OBP, and therefore the up-converters and receiversbecome optional.

According to an aspect of the present invention there is provided ahigh-power flexible-polarization satellite payload system for satellitecommunications, the system comprising:

-   -   a centralized On-Board Processor (OBP) connecting to a transmit        chain having a first and a second transmit paths and a receive        chain having a first and a second receive paths, said first        transmit and first receive paths connecting to a first        transmit/receive duplexer, said second transmit and second        receive paths connecting to a second transmit/receive duplexer,        said first and second transmit/receive duplexer connecting to a        two polarization antenna for transmitting and receiving signals;    -   said first and second transmit paths transmitting an in-phase        and a quadrature phase output signals, respectively, said first        and second receive paths receiving an in-phase and a quadrature        phase input signals, respectively; and    -   a phase-tracked apparatus adjusting a respective phase and/or        amplitude of said in-phase and quadrature phase output signals        in said transmit chain for power combination of said in-phase        and quadrature phase output signals at said two-polarization        antenna, and a respective phase of said in-phase and quadrature        phase input signals in said receive chain.

In one embodiment, the phase-tracked apparatus includes, in each saidfirst and second receive paths, a fixed phase adjuster (or trimmer)connected between a quadrature hybrid coupler and a respective one ofsaid first and second transmit/receive duplexers.

Conveniently:

-   -   said transmit chain includes, in each said first and second        transmit paths, a phase-tracked up-converter connecting to the        OBP and connected to a phase-tracked high-power amplifier        connected to a phase-tracked filter connecting to a respective        said first and second transmit/receive duplexers, and said        receive chain includes either a polarization selection switch        connected to a common input filter connected to a common        receiver connecting to the OBP or, for each said first and        second receive paths, an input filter connected to a receiver        connecting to the OBP;    -   and wherein said phase-tracked apparatus includes a frequency        generation unit connecting to the OBP and providing a respective        phase-tracked local oscillator signal to each said phase-tracked        up-converters and either a local oscillator signal to said        common receiver or a respective local oscillator signal to each        said receiver, respectively.

Alternatively:

-   -   in said transmit chain, said OBP connects to either, in each        said first and second transmit paths, an up-converter connecting        to, or a common up-converter connecting to a quadrature hybrid        connecting to, in each said first and second transmit paths, a        gain & phase adjuster connecting to a phase-tracked high-power        amplifier connected to a phase-tracked filter connecting to a        respective said first and second transmit/receive duplexers;    -   and wherein, in said receive chain, said quadrature hybrid        coupler connects to either a polarization selection switch        connected to a common input filter connected to a common        receiver connecting to the OBP or, for each said first and        second receive paths, an input filter connected to a receiver        connecting to the OBP.

In one embodiment, the OBP determines the polarization of at least oneof said in-phase and a quadrature phase output signals of the first andsecond transmit paths and said in-phase and a quadrature phase inputsignals of the first and second receive paths.

In one embodiment, at least one of the transmit and receive chainsincludes a polarization selection switch.

In one embodiment, the said OBP determines the polarization of one ofsaid in-phase and a quadrature phase output signals of the first andsecond transmit paths and said in-phase and a quadrature phase inputsignals of the first and second receive paths, and the other one of thetransmit and receive chains includes a polarization selection switch.

In one embodiment, the system further includes a telecommand satellitelink communicating with a ground station receiving said powercombination of said in-phase and quadrature phase output signals, saidground station including:

-   -   a measurement unit receiving the power combination of said        in-phase and quadrature phase output signals and measuring        cross-polarization discrimination and/or axial ratio performance        of the system;    -   a ground computing unit receiving and analyzing the measured        system performance from the measurement unit by determining if        the measured performance is either within a predetermined        requirement range or performance optimization reachable to stop        calibration, and, if not, generating a command signal with        compensation adjustments of respective said phase and/or        amplitude of said in-phase and quadrature phase output signals        for up-link communication of said command signal via the        telecommand satellite link.

Conveniently, the performance optimization being reachable is determinedusing a search method to iteratively optimizing the measured systemperformance.

According to another aspect of the present invention there is provided amethod of calibrating a high-power flexible-polarization satellitepayload system as claimed in claim 1, the method comprising the stepsof:

-   -   measuring cross-polarization discrimination and/or axial ratio        performance of the system on the ground;    -   determining if the measured system performance is within a        predetermined requirement range to stop calibration, if not,        iteratively optimizing the measured system performance and        determining if optimum system performance is reachable to stop        calibration, and, if not, generating a command signal with        compensation adjustments of respective said phase and/or        amplitude of said in-phase and quadrature phase output signals;        and    -   up-linking said command signal to the system via telecommand        satellite link and repeating the preceding steps.

Conveniently, iteratively optimizing is performed using a search method.

Conveniently, the search method is one of a pattern search, atrust-region search, and a line search.

Other objects and advantages of the present invention will becomeapparent from a careful reading of the detailed description providedherein, with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the present invention will becomebetter understood with reference to the description in association withthe following Figures, in which similar references used in differentFigures denote similar components, wherein:

FIG. 1 is a schematic block-diagram of a generic communication payloadof the prior art with Transmit & Receive chains and a dual-polarizationantenna.

FIG. 2 is a schematic block-diagram for high-power flexible-polarizationpayload application with a polarization selection switch on the receivepath in accordance with an illustrative embodiment of the presentinvention.

FIG. 3 is a schematic block-diagram for high-power flexible-polarizationpayload application with the receive path polarization selected by theOBP in accordance with another illustrative embodiment of the presentinvention.

FIG. 4 is a schematic block-diagram for high-power flexible-polarizationpayload application. Gain & phase adjusters are present in the transmitpaths. Both transmit and receive path polarizations are selected by aswitch in accordance with another illustrative embodiment of the presentinvention.

FIG. 5 is a schematic block-diagram for high-power flexible-polarizationpayload application. Gain & phase adjusters are present in the transmitpath. The receive path polarization is selected by the OBP and thetransmit path polarization is selected by a switch in accordance withanother illustrative embodiment of the present invention.

FIG. 6 is a schematic block-diagram for high-power flexible-polarizationpayload application. Gain & phase adjusters are present in the transmitpath. The transmit path polarization is selected by the OBP and thereceive path polarization is selected by a switch in accordance withanother illustrative embodiment of the present invention.

FIG. 7 is a schematic block-diagram for high-power flexible-polarizationpayload application. Gain & phase adjusters are present in the transmitpath. The transmit and receive path polarizations are both selected bythe OBP in accordance with another illustrative embodiment of thepresent invention.

FIG. 8 is a schematic block-diagram of the calibration scheme forhigh-power flexible-polarization payload application. FIG. 8 is similarto FIG. 2 herein with the addition of illustration oftelemetry/telecommand (TM/TC) link and ground system.

FIG. 9 is an illustration showing the payload calibration algorithm usedin conjunction with the block-diagram of FIG. 8. By ground measurementsof XPD/AR, this algorithm can be used to adjust (if necessary) thepayload gain & phase to meet the system requirements.

FIG. 10 is a schematic block-diagram similar to FIG. 2, for high-powerflexible-polarization payload application with a polarization selectionswitch on the receive path in accordance with another illustrativeembodiment of the present invention in which the OBP directly processesthe RF signals.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the annexed drawings the preferred embodiment of thepresent invention will be herein described for indicative purpose and byno means as of limitation.

FIGS. 2 to 8 show different illustrative embodiments 10 of schematicblock-diagrams of high-power (typically above 200 Watts)flexible-polarization communication antenna systems for spacecrafts withTransmit (TX) 12 & Receive (RX) 14 chains payload in accordance with thepresent invention.

FIG. 2 is a schematic block-diagram for high-power flexible-polarizationpayload application with a polarization selection switch 109 on thereceive chain 14 in accordance with an illustrative embodiment of thepresent invention. The transmit chain 12 polarization is defined by theOn-Board Processor (OBP) I & Q (In-phase & Quadrature phase) outputswhich have their own separate transmit paths 12 a, 12 b. Each transmitpath comprises an upconverter 102 a, 102 b, high-power amplifier 103 a,103 b and output filter 104 a, 104 b. A duplexer 105 a, 105 b is used tosegregate the TX and RX chains near the antenna 106. Both receive paths14 a, 14 b of the receive chain 14 have fixed phase adjusters ortrimmers 107 a, 107 b and are combined in a quadrature hybrid 108. Aswitch 109 is typically used to select which branch of the hybrid isused and, at the same time, which polarization is selected. The RXsignal 26 is then filtered by an input filter 110 before entering thereceiver 111.

Phase tracking, via a phase-tracked apparatus, is mandatory between theI & Q signals in the transmit paths 12 a, 12 b. Phase tracking is alsonecessary for the associated Local Oscillator (LO) signals 29 a-29 cused in the frequency conversion and generated by the FrequencyGeneration Unit (FGU) 115 of the present embodiment. This FGU unit 115is used to generate the LO signals of the frequency translationperformed by the upconverters 102 a, 102 b and receiver 111.

An in-orbit calibration is performed by adjusting the OBP I & Q outputsignals. The actual calibration scheme and algorithm are describedherein below and on FIGS. 8 and 9.

FIG. 3 is a schematic block-diagram for high-power flexible-polarizationpayload application with the receive path polarization selected by theOBP 101 in accordance with a second illustrative embodiment. This OBPreceive chain 14, with each receive path 14 a, 14 b includes an inputfilter 110 a, 110 b and a receiver 111 a, 111 b (each connected to theFGU 115 to receive their respective LO signal 29 a′, 29 a″), is whatdiffers the block-diagram of FIG. 3 with the previous one of FIG. 2. Thelatter was using a selection switch 109 in the receive chain. Theremaining constituents of FIG. 3 are the same as FIG. 2. Refer to itsdescription and functions in the text above.

The advantages of OBP selection are typically in two folds: one is theimproved gain-over-temperature (G/T) performance with the removal of theselection switch in the RX RF chain. The second advantage is that theremoval of the RF selection switch 109 could reduce the loss of the RXsignal during switching. On the other hand, an OBP selectiondisadvantage is the increased hardware complexity with an additionalfilter and receiver.

FIG. 4 is a schematic block-diagram for high-power flexible-polarizationpayload application. Gain & phase adjusters 116 a, 116 b are present inthe transmit paths 12 a, 12 b. Both transmit and receive pathpolarizations are selected by a switch 109′, 109 in accordance withanother illustrative embodiment. Both transmit 12 and receive 14 chainshave a switch 109′, 109 and quadrature hybrid 108′, 108 to allowpolarization selection while using only one receiver 111 andup-converter 102. This transmit signal 30 is treated by the commonup-converter 102 which translates the low frequency of the OBP output toTX frequency (if needed), and performs suitable signal conditioning onthe RF/microwave signal 36. Then the switch 109′ selects thepolarization of the signals 37 a, 37 b entering the quadrature hybrid108′ for phase conditioning of the transmit I & Q signals 38 a, 38 b.The receive paths 14 a, 14 b have fixed phase adjustments 107 a, 107 b.The transmit I & Q paths 12 a, 12 b have gain & phase adjusters 116 a,116 b before the high-power amplifiers 103 a, 103 b. The receive 22 a,22 b and transmit 33 a, 33 b signals are segregated by a duplexer 105 a,105 b in a similar manner as other payload systems described herein.

Phase tracking is mandatory between the I & Q signals 38 a, 38 b in thetransmit paths 12 a, 12 b. These I & Q signals 38 a, 38 b are associatedto the quadrature hybrid output ports. Both transmit paths 12 a, 12 bfrom the quadrature hybrid 108′ must phase track over life andtemperature.

The in-orbit calibration is performed by the gain & phase adjusters 116a, 116 b in both I & Q transmit paths 12 a, 12 b. These adjusters 116 a,116 b can vary both amplitude and phase of the passing transmit signal.In other payload systems described previously, this gain & phaseadjustment function was performed by the OBP (refer to FIGS. 2 and 3).The calibration algorithm is typically the same as other payload systemblock-diagrams herein and is described on FIG. 9.

FIG. 5 is a schematic block-diagram for high-power flexible-polarizationpayload architecture. Gain & phase adjusters 116 a, 116 b are present inthe transmit chain 12. The receive path polarization is selected by theOBP 101 and the transmit path polarization is selected by a switch 109′in accordance with another illustrative embodiment.

The detailed description of FIG. 5 is the same as FIG. 4 with theexception that receive selection switch 109 is removed and its functionreplaced by an extra function within the OBP 101. The latter selectswhich of the two polarizations is used in the receive chain 14. Phasetracking requirements are typically the same as described in FIG. 4detailed description. In-orbit calibration is also the same as describedin FIG. 4 detailed description.

Compared with FIG. 4, the advantages of the RX chain 14 is the improvedG/T performance due to the removal of the RF switch 109 and the reducedloss of the RX signal during switching. However, a disadvantage is thecost of an additional filter and receiver.

FIG. 6 is a schematic block-diagram for high-power flexible-polarizationpayload application. Gain & phase adjusters 116 a, 116 b are present inthe transmit paths 12 a, 12 b. The transmit path polarization isselected by the OBP 101 and the receive path polarization is selected bya switch 109 in accordance with another illustrative embodiment.

The detailed description of FIG. 6 is the same as FIG. 4 with theexception that transmit selection switch 109′ is removed and itsfunction replaced by an extra function within the OBP 101. The latterselects which of the two polarization is used in the transmit chain 12.Phase tracking requirements are typically the same as described in FIG.4 detailed description. In-orbit calibration is also the same asdescribed in FIG. 4 detailed description.

Compared with FIG. 4, the advantage of the TX chain 12 is the capabilityof seamless polarization selection switching by the OBP 101. However, adisadvantage is the cost of an added up-converter.

FIG. 7 is a schematic block-diagram for high-power flexible-polarizationpayload application. Gain & phase adjusters 116 a, 116 b are present inthe transmit paths 12 a, 12 b. The transmit and receive pathpolarizations are both selected by the OBP 101 in accordance withanother illustrative embodiment.

The detailed description of FIG. 7 is the same as FIG. 4 with theexception that both transmit and receive selection switches 109′, 109are removed and their functions replaced by the OBP 101. The latterselects which of the two polarizations is used in the transmit 12 a, 12b and receive 14 a, 14 b paths. Phase tracking requirements aretypically the same as described in FIG. 4 detailed description. In-orbitcalibration is also the same as described in FIG. 4 detaileddescription.

Compared with FIG. 4, the advantage of the TX chain 12 is the capabilityof seamless polarization selection switching by the OBP 101 with thecost of an added up-converter. The advantages of the RX chain 14 are theimproved G/T performance and the reduced loss of the RX signal duringswitching with the cost of an additional filter and receiver.

FIG. 8 is a schematic block-diagram of the calibration scheme forhigh-power flexible-polarization payload application. The satellitepayload may be any one of the embodiments described earlier in FIGS. 2to 7. In FIG. 8, the payload configuration of FIG. 2 is taken herein asan example with the addition of details on telemetry/telecommand (TM/TC)40 and ground system.

Signals 21 & 35, 22 a & 34 a, 22 b & 34 b follow the same paths and arecommon to both receive and transmit operations, respectively. Typically,this is an RF/microwave signal which conveys binary data on aband-limited modulated carrier.

In transmit, the signals 34 a, 34 b, suitable for polarization X and Yrespectively (typically, orthogonal linear polarizations), are combinedwithin the antenna 106 and emitted with the suitable polarization(typically, left-handed or right-handed circular polarization) from thesatellite payload to a terminal or ground station 112 on earth.

In receive, the receive input signal 21 is separated into signals 22 a,22 b, which relative amplitude and phase is directly related to thesignal 21 polarization received by the antenna 106 (typically,left-handed or right-handed circular polarization). The duplexers 105 a,105 b allow separating the transmit signals from the receive signal byfrequency-division duplexing, time-division duplexing, or halfduplexing, and the received signals 22 a, 22 b are thus routed to thereceive paths 14 a, 14 b, as signals 23 a, 23 b. The fixed phaseadjustment 107 a, 107 b allows to compensate (equalize) the transmissionphase of each receive signal paths to form signals 24 a, 24 b, whichpreserve the phase relation of signals 22 a, 22 b. The phase compensatedsignals 24 a, 24 b are combined in the quadrature hybrid 108 to form thetwo circularly polarized signals 25 a, 25 b, which is then selected byswitch 109. The selected signal 26 is then subject to filtering via aninput filter 110. The filtered signal 27 is then accepted by thereceiver 111 which normally performs low-noise amplification anddown-conversion to a lower intermediate frequency (IF), as signal 28.This intermediate frequency is again received by the OBP 101 fordemodulation, data extraction and data regeneration as needed. TheFrequency Generation Unit (FGU) 115 generates signals 29 b, 29 c and 29a which are the local oscillator (LO) signals of the frequencytranslation performed by the upconverters and receiver (102 a, 102 b and111), respectively. Signals 29 b-29 c are phase tracked signals. Signal29 d is also generated by the FGU 115. Signal 29 d is the clock signalfor the OBP 101 and it is synchronous to the other FGU local oscillatorsignals.

In transmit, the OBP 101 formats the data and typically provides an “I”and “0” output (signals 30 a, 30 b) which can be under the form of (butnot limited to) digital data stream, or an intermediate frequency analogband-limited signal. This signal 30 a, 30 b is treated by thephase-tracked up-converter 102 a, 102 b which performs low frequency toTX frequency conversion (if needed), and performs suitable signalconditioning to generate the RF/microwave signal 31 a, 31 b. This signal31 a, 31 b is normally at a low amplitude (typically below 1 Watt) andtherefore needs further amplification to higher power. This is typicallydone using the high-power amplifier 103 a, 103 b, and signal 32 a, 32 bresults. This high-power RF signal 32 a, 32 b requires filtering inorder to ensure the removal of harmonics, and out-of-band noise &spurious, created by the high-power amplifier. This function isperformed by the output filter 104 a, 104 b, and the filtered high-powersignal 33 a, 33 b is fed to the duplexer 105 a, 105 b to be transmittedto the antenna 106 (signal 34 a, 34 b), where they get combined asoutput signal 35.

The flexible polarization payload is typically commandable andprogrammable via the ground system. This ground system comprises of theground station 112 and computer 113 in addition to thecross-polarization discrimination (XPD) and/or the Axial Ratio (AR)measurement system 114.

This ground system performs the XPD/AR measurements, checks ifrequirements are met and, if necessary, calculates and sends gain &phase adjustment commands to the payload, via the TM/TC satellite link(signal 40).

FIG. 9 is a schematic showing the payload calibration algorithm used inconjunction with the block-diagram of FIG. 8. By ground measurements ofXPD/AR, this algorithm adjusts (if necessary) the payload gain & phaseto meet the system requirements.

The calibration algorithm starts by the measurements of thecross-polarization discrimination (XPD) and/or Axial Ratio (AR). Itfirst checks if the requirement is met. If so, no action is performed.When the requirement is not met, the algorithm iteratively tries tooptimize XPD/AR using a search method. This search method can be apattern search, trust-region search, line search or any another type ofsearch method. If the iterations have not reached an optimumperformance, gain & phase adjustment commands are generated and sent tothe communication payload as shown on FIG. 9. Once the iterations havereached the optimum performance, the XPD/AR performance should have beenoptimized and the algorithm stops no matter the requirement is met ornot in order to avoid an endless iteration loop.

FIG. 10 refers to a schematic block-diagram for high-powerflexible-polarization payload application in accordance with anotherillustrative embodiment 10′ similar to the embodiment of FIG. 2,although it could also similarly be implemented with any otherembodiment. In this embodiment, the OBP 101 directly processes theRF/microwave signals, such that the upconverter(s) in the TX chainand/or the downconverter (s) (typically incorporated into thereceiver(s)) in the RX chain are not required. Accordingly, in the RXchain 14, low-noise amplifier(s) (LNAs) 117 is/are therefore required toaccount for the replacement of the receiver(s) 111. Similarly, thiswould be applicable in all embodiments with the OBP directly processingthe RF/microwave signals. In this specific embodiment, a sampling clock118 is also required in replacement Frequency Generation Unit 115 toensure that a clock signal 29 d is provided to the OBP 101 foranalog-to-digital and digital-to-analog conversion of all RF/microwavesignals.

Although the present invention has been described with a certain degreeof particularity, it is to be understood that the disclosure has beenmade by way of example only and that the present invention is notlimited to the features of the embodiments described and illustratedherein, but includes all variations and modifications within the scopeof the invention as hereinabove described and hereinafter claimed.

We claim:
 1. A high-power flexible-polarization satellite payload systemfor satellite communications, the system comprising: a centralizedOn-Board Processor (OBP) connecting to a transmit chain having a firstand a second transmit paths and a receive chain having a first and asecond receive paths, said first transmit and first receive pathsconnecting to a first transmit/receive duplexer, said second transmitand second receive paths connecting to a second transmit/receiveduplexer, said first and second transmit/receive duplexer connecting toa two polarization antenna for transmitting and receiving signals; saidfirst and second transmit paths transmitting an in-phase and aquadrature phase output signals, respectively, said first and secondreceive paths receiving an in-phase and a quadrature phase inputsignals, respectively; and a phase-tracked apparatus adjusting arespective phase and/or amplitude of said in-phase and quadrature phaseoutput signals in said transmit chain for power combination of saidin-phase and quadrature phase output signals at said two-polarizationantenna, and a respective phase of said in-phase and quadrature phaseinput signals in said receive chain.
 2. The system of claim 1, whereinsaid phase-tracked apparatus includes, in each said first and secondreceive paths, a fixed phase adjuster connected between a quadraturehybrid coupler and a respective one of said first and secondtransmit/receive duplexers.
 3. The system of claim 2, wherein: saidtransmit chain includes, in each said first and second transmit paths, aphase-tracked up-converter connecting to the OBP and connected to aphase-tracked high-power amplifier connected to a phase-tracked filterconnecting to a respective said first and second transmit/receiveduplexers, and said receive chain includes either a polarizationselection switch connected to a common input filter connected to acommon receiver connecting to the OBP or, for each said first and secondreceive paths, an input filter connected to a receiver connecting to theOBP; and wherein said phase-tracked apparatus includes a frequencygeneration unit connecting to the OBP and providing a respectivephase-tracked local oscillator signal to each said phase-trackedup-converters and either a local oscillator signal to said commonreceiver or a respective local oscillator signal to each said receiver,respectively.
 4. The system of claim 2, wherein: in said transmit chain,said OBP connects to either, in each said first and second transmitpaths, an up-converter connecting to, or a common up-converterconnecting to a quadrature hybrid connecting to, in each said first andsecond transmit paths, a gain & phase adjuster connecting to aphase-tracked high-power amplifier connected to a phase-tracked filterconnecting to a respective said first and second transmit/receiveduplexers; and wherein, in said receive chain, said quadrature hybridcoupler connects to either a polarization selection switch connected toa common input filter connected to a common receiver connecting to theOBP or, for each said first and second receive paths, an input filterconnected to a receiver connecting to the OBP.
 5. The system of claim 1,wherein said OBP determines the polarization of at least one of saidin-phase and a quadrature phase output signals of the first and secondtransmit paths and said in-phase and a quadrature phase input signals ofthe first and second receive paths.
 6. The system of claim 1, wherein atleast one of the transmit and receive chains includes a polarizationselection switch.
 7. The system of claim 1, wherein said OBP determinesthe polarization of one of said in-phase and a quadrature phase outputsignals of the first and second transmit paths and said in-phase and aquadrature phase input signals of the first and second receive paths,and the other one of the transmit and receive chains includes apolarization selection switch.
 8. The system of claim 1, furtherincluding a telecommand satellite link communicating with a groundstation receiving said power combination of said in-phase and quadraturephase output signals, said ground station including: a measurement unitreceiving the power combination of said in-phase and quadrature phaseoutput signals and measuring cross-polarization discrimination and/oraxial ratio performance of the system; a ground computing unit receivingand analyzing the measured system performance from the measurement unitby determining if the measured performance is either within apredetermined requirement range or performance optimization reachable tostop calibration, and, if not, generating a command signal withcompensation adjustments of respective said phase and/or amplitude ofsaid in-phase and quadrature phase output signals for up-linkcommunication of said command signal via the telecommand satellite link.9. The system of claim 8, wherein said performance optimization beingreachable is determined using a search method to iteratively optimizingthe measured system performance.